The present invention relates to stuffed, sealed, multi-ply envelope assemblies or "mailers". More particularly, the invention is directed to mailers which use carbonless paper in a chemical imaging system and in which pressure or impact is relied upon to cause two different coatings on adjacent sheets of a multi-ply assembly to react chemically to generate visual indicia corresponding in configuration to the impact pattern, as a faithful copy thereof.
Multi-ply mailers of the general type indicated are well known in the art. Typically, a "top" sheet is coated on its back (CB sheet) with microscopic capsules of a dye, the dye being in a colorless form. A "bottom" sheet is coated on its front (CF sheet) with a chemical activator. The dye remains colorless until, through pressure or impact, the rupturable capsules are broken or fractured permitting the dye to interact chemically with the activator so that a colored form of the dye is generated, thus providing a desired visual image.
Intermediate plies of the multi-ply mailer assembly are coated front and back (CFB sheets) so that each bottom-coated sheet mates with a respective top-coated sheet therebeneath to generate visual images on the top surface of each of the racked sheets in the stacked multi-ply assembly or mailer.
In some prior art mailers the indicia-generating chemical components, including the pressure-rupturable dye capsules and the color-developing acceptor are contained in a single coating.
Formulations for and methods for producing coating compositions containing pressure-rupturable micro-capsules of a colorless dyestuff precursor and coating compositions containing a color developer or dyestuff acceptor, or dye-activating or converting chemical agent are known in the art. Neither the formulations nor their methods of manufacture constitute elements of the present invention.
Processes for the production of coating compositions containing dye microcapsules and for applying the coating compositions to a paper substrate are described in Yoshida and Brabender U.S. Pat. No. 4,985,484 issued Jan. 15, 1991. The entire disclosure of that patent is hereby specifically incorporated herein by reference, to the extent it is not inconsistent herewith. The activator may consist of hot melt flakes of wax-like consistency and properties, with chemical additives. Application is made in the melted form.
Coating composition for producing image forming receptor coatings for reacting with the dye from the fractured microcapsules are also well known and are adequately described in issued patents including Chang U.S. Pat. B1 4,425,386 issued Mar. 29, 1988. The disclosure is hereby specifically incorporated herein by reference, to the extent it is not inconsistent herewith.
The activator compositions may be applied to paper substrates from a melted wax system using a hot melt coater which applies the melt to the press plate rolls of a printer machine. Coating of the press is also feasible.
Liquid coating systems containing encapsulated chromogenic dyes may be employed. These systems are either water based, or of a non-aqueous type.
Suitable compositions and the coating equipment employed to produce carbonless papers are described in technical literature readily available from The Mead Corporation of Dayton, Ohio, for example, their OPAS.RTM. (on/off Press Application System) liquid coating system, materials and equipment. In the light of the above and other extensive and readily available patents, published articles, and promotional literature, no further or detailed treatment of these areas is deemed necessary herein.
It is in the addressing of mailers of the type described above that the present invention finds special utility, particularly where the addressing is carried out automatically as with a computer-controlled machine involving a line printer. A widespread practice in the prior art is to deposit a CB coating on the back of the plies and a CF coating on the face, using the OPAS system described. In this arrangement, the top sheet or file copy is used primarily for selective transfer of the address to the outgoing envelope, and secondarily, as a file copy. Most companies have no need for a "file copy", since their computer stores the data on magnetic tape. It would, therefore, be desirable to eliminate this extraneous or unneeded sheet. The described simplification and elimination of the superfluous cover sheet are achieved in accordance with the practice of the present invention.
In one prior art method a system for image transfer which does not require a cover or top sheet relies upon a self-contained carbonless patch that is printed on the face of the outgoing envelope. Coating components react upon impact to create the "image". A disadvantage of this system is a tendency to produce smudging or objectional spurious markings resulting from unavoidable physical handling and postal processing of the mailer. In some cases the imprinted address indicia themselves tend to be obscured, rendered quite illegible, or even obliterated. Moreover, the self-contained coating material has an objectionally short shelf life.
Neubauer U.S. Pat. No. 4,729,506 entitled, "Mailer with Transparent Patch" describes a window envelope structure in which a transparent, window-closing patch is adhesively secured to a top panel of the mailer on an underside thereof.
The coating, cutting, bonding and collating steps which must be carried out to produce such a mailer are complex. The procedures are time-consuming and costly, calling for highly specialized equipment and for specially trained personnel to operate the equipment. The "patch" product does not lend itself to production utilizing the computer-controlled line ordinarily employed to fabricate mailers.
In marked contrast, the mailer of the present invention uses a physically separate and independent full web, panel or sheet contained within the window envelope assembly itself. Preferably, the entire areal expanse of this separate sheet is coated for impact imprinting, in selectable areas--a valuable option unavailable in the prior art. The transparent window sheet of the present invention is readily collated, as an additional sheet or web, with the other parts of the mailer. No special steps or equipment are required.
A principal aim of the present invention is to avoid the above-described short-comings and objectionable features of prior art mailers, particularly in the manner in which such mailers are addressed, and to provide improved structures and methods ensuring savings in material and resulting in enhanced and more reliable imprinted legends or indicia.